Digital camera system with piezoelectric actuators

ABSTRACT

A digital camera is constructed with multiple lenses mounted in a pair of tubular elements which are nested together for relative axial movement. Movement is provided by piezoelectric actuators mounted externally to a support tube on flexible printed circuit board elements. Each lens tube is provided with a drive rail which extends at least partially over the length of the lens tube and projects radially outward from the periphery of each of the tubes. The rails are accessible to the engagement pads of the piezoelectric actuators to allow the transmission of drive forces to each of the tubes.

RELATED APPLICATIONS

[0001] This application is a continuation in part application based onU.S. application for patent, Ser. No. 10/163,111, filed on Jun. 5, 2002and Applicant claims priority thereof.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an assembly of opticalcomponents for a miniature digital camera, including piezoelectricactuators for moving the optical components to provide focusing, zoom,and other functions. In particular an arrangement of the components isdescribed that reduces the overall size and facilitates assembly.

[0004] 2. Brief Description of Related Developments

[0005] The components of electronic cameras require low powerconsumption, low weight and cost efficiency. These design criteria arechallenged by the demand for optically adjustable cameras that provideautofocus, zoom optics, or both. These features require the relativemovement of optical elements to provide the adjustment. The requiredmotion is typically linear but may use a rotating motor combined with amotion-converting mechanism such as a lead-screw. The motion range isoften in the order of millimeters. It is a purpose of this invention toprovide a mechanism for adjusting the position of the optical elementsin an electronic camera.

[0006] One component that has been used in numerous applications is abimorph piezoelectric element, such elements are constructed of multiplelayers of piezoelectric material wherein each layer is connected forindependent excitation. In U.S. Pat. No. 4,291,958, a bimorphpiezoelectric cantilever beam is used in combination with a magnifyinglever for focusing a camera. However, the necessary stroke of such afocusing device results in a poor stiffness of the device. In electroniccamera applications, space is a crucial factor. There is thus a need forsimple drive elements that can operate in narrow spaces with limitedmechanical support. It is a purpose of this invention to utilize abimorph piezoelectric element to adjust the position of a lens in anoptical system of a digital camera.

[0007] A camera system using a piezoelectric actuator is described incommonly owned, related application for patent, Ser. No. 10/163,111referenced above. The disclosure of this application is incorporatedherein by reference. In this application, a lens element is mountedwithin a camera on a tubular member. The lens tube is in turn mounted ona support tube for movement along the longitudinal axis of the tubularmember. The adjustment movement is provided by means of multiple bimorphpiezoelectric elements, for example by three elements, spacedsymmetrically around the circumference of the support tube. Thepiezoelectric elements are connected to and mounted on a flexibleprinted circuit board which may contain other electronic componentsassociated with the lens drive system. The flexible printed circuitboard is mounted on the support tube and is in turn connected to avoltage source such as a battery. The flexibility of the printed circuitboard allows it to be formed to the shape of the support tube and forthe piezoelectric element to be positioned in engagement with the lenstube.

[0008] The bimorph piezoelectric element used in the mechanism of thecited application is constructed of at least two layers of piezoelectricmaterial which are independently energized to provide relativedeformation between the two layers. This piezoelectric element is formedin the shape of a beam having an engagement pad extending transverse tothe plane of the element from its midpoint. The beam is fixed to thecircuit board close to ends or nodal positions. The beam comprises apair of bimorph piezoelectric elements extending to either side of theengagement pad. Each of the bimorph elements has dual active layers. Thedifferential deformation generated by energizing only one of the twolayers will cause the piezoelectric elements to bend, moving the outerend of the engagement pad into contact with the movable lens tube. Byaltering the excitation of the piezoelectric elements, the engagementpad causes movement in an axial direction, thereby adjusting theposition of the lens. A pattern of excitation is devised to providemovement in discrete steps.

[0009] In the system of the cited application, a processor is connectedin the printed circuit board to provide the main control for the digitalcamera and is constructed to generate a drive voltage pattern inaccordance with the desired movement of the lens.

[0010] The movement generated by the piezoelectric element provides ahigh resolution, but there are no structural features that provide areference in order to obtain accurate repeatability. The step lengthprovided by the piezoelectric element can vary with operational andenvironmental conditions. In order to obtain the precision required insome optical designs, a position sensor is used to monitor the positionof the movable tubes. An optical sensor is used to view a reflectingsurface, which is mounted on the moveable tube. The reflecting surfaceconsists of a gray-scale incorporated into the surface treatment of themoveable tube. This configuration will provide accurate positionalmonitoring of a moveable tube.

[0011] It is a purpose of this invention to provide a miniature digitalcamera system of the type described above in which the components arearranged to facilitate their assembly in an over all package that issmaller. It is another purpose of this invention to provide a railsystem external to the lens support tubes for engagement bypiezoelectric actuators.

SUMMARY OF THE INVENTION

[0012] A digital camera is constructed with multiple lenses mounted in apair of tubular elements, which are nested together for relative axialmovement to provide a zoom function. The lens tube assembly is in turnmounted on a support tube. The lens tube assembly is moveable withinsaid support tube with respect to an image plane to provide an autofocusfunction. Movement is provided by piezoelectric actuators mountedexternally to the support tube on flexible printed circuit boardelements. Each lens tube is provided with a drive rail which extends atleast partially along the length of the lens tube and project radiallyoutward from the periphery of each of the tubes. The rails areaccessible to the engagement pads of the piezoelectric actuators toallow the transmission of drive forces to each of the tubes. Slots areconstructed in the support tube to allow the drive rails to projectthrough the support tube. The piezoelectric actuators are mounted topermit engagement by a pair of actuators on either side of the rail.

[0013] The rails are constructed having a wedge shaped cross sectionwhich narrows radially inward towards the axis of the system. Thepiezoelectric elements are mounted on opposing surfaces of U-shapedflexible printed circuit boards with a rail in between. In this manner,the piezoelectric elements are positioned for engagement with thetapered sides of the rail. A mounting bracket is provided in which issecured the printed circuit board. The clip like mounting bracket exertsa spring force on the printed circuit board or the piezoelecric elementitself to bias the piezoelectric elements into engagement with the rail.This bias force also has a radial component which is applied outward onthe tube element to maintain the tubes in axial alignment and minimizefunction effects. Position sensors are mounted on the U-shaped printedcircuit board in optical communication with reflective surfaces ofrespective lens tubes.

[0014] In one embodiment, the rails are positioned concentrically on thetube assembly. In a second embodiment the rails are positioned in thesame quadrant of the tube assembly circumference. In the latterembodiment the engagement forces are applied eccentrically to the tubeelements. To assist in maintaining tube alignment, wedge shaped groovesand mating surfaces are formed on the engaging surfaces of the lens tubeassembly and the support tube.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The digital camera system of this invention is explained in moredetail below with reference to the accompanying drawing, in which:

[0016]FIG. 1 is an axially exploded, perspective view of an embodimentof a camera system, according to this invention;

[0017]FIG. 2 is an enlarged, exploded perspective view of the lenselements of FIG. 1;

[0018]FIG. 3 is an enlarged exploded, perspective view of thepiezoelectric drive system of FIG. 1;

[0019]FIG. 4a is a transverse sectional view of the embodiment of thisinvention shown in FIG. 1, taken along section lines A-A of FIG. 4b;

[0020]FIG. 4b is a side view of the assembled optical assembly of FIG.1;

[0021]FIG. 5 is an axially exploded, perspective view of an embodimentof a camera system, according to an alternative embodiment of thisinvention; and

[0022]FIG. 6 is a transverse sectional view of the alternate embodimentof this invention shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] Referring to FIG. 1, a digital camera 1 is constructed with apair of lens systems 2 and 3 mounted in a pair of tubular elements 4 and5. Lens tubes 4 and 5 are nested together for relative movement alongaxis x-x to provide a multiple optical functions, such as auto focus andzoom. The assembled lens tubes 4 and 5, assembly 6, is in turn mountedon a support tube 7 for axial movement within said support tube 7 withrespect to an image plane 8. A filter 9 may be positioned in front ofimage plane 8. An image sensor 10 is mounted on main circuit board 11 onwhich may also be mounted the control and processing components of thedigital camera. Lens tubes 2 and 3 may have multiple cooperating lensmounted within.

[0024] Support tube 7 is constructed to receive the lens tubes 4 and 5in an interior passage 12. Movement is provided by piezoelectricactuators 13-16 mounted externally to the support tube on flexibleprinted circuit board elements 17 and 18. Spring clip mounting brackets19 and 20 secure the piezoelectric modules in place within a cover tube21.

[0025] Referring to FIG. 2, lens tubes 4 and 5 are nested together forsliding movement. As shown lens tube 5 is constructed with roundedsurfaces 22 provided on the outer periphery of a trio of projections23-25. The projections 23-25 extend through mating slots 26-28 in lenstube 4. Slots 26-28 are constructed with tapered surfaces 29 whichengage opposing tapered surfaces 30 on projections 23-25.

[0026] Each of lens tubes 4 and 5 is provided with a drive rail 31 and32 respectively which extends at least partially over the length of thelens tubes 4 and 5 and project radially outward from the periphery ofeach of the tubes. As shown in FIG. 3, the rails 31 and 32 areaccessible to the engagement pads 33-36 of the piezoelectric actuators13-16 to allow the transmission of drive forces to each of the tubes 4and 5. Slots 37 are constructed in the support tube 7 to allow the driverails 31 and 32 to project through the support tube 7.

[0027] As shown in FIG. 3, the piezoelectric actuators 13-16 areindependently mounted on a flexible printed circuit board 38 and 39.Printed circuit boards 38 and 39 are formed in the shape of a U havingopposing arms 40 and 41. The printed circuit board is constructed havingcircuit paths (not shown) to supply power to the piezoelectric actuators13-16. Optical sensors 42 and 43 may also be fixed to the printedcircuit boards 38 and 39. As shown, the actuators 13-16 are mounted inpairs on opposing arms 40 and 41. The assembly is fixed to the supporttube 7 in a position to permit engagement by a pair of actuators, suchas 15 and 16, on either side of the rails 31 and 32.

[0028] Lens tubes 4 and 5 have to be aligned with the support tube 7with minimum friction forces. The friction forces will result in atorque that tend to rotate the lens tube away from axial alignment. Ifthe supporting surfaces between the lens tubes 4 and 5 and thesupporting tube 7 are very close to, or centered with, the engagementpads of the drive elements, the torque will be reduced due to a shortertorque lever. To maintain these advantageous conditions the lens tubes 4and 5 have to be pressed against the supporting tube 7 with a controlledforce. This desired bias force in the radial direction can be created byseveral means with their respective advantages and disadvantages. Thebias force can be achieved by a flexible spring (not shown) of e.g.steel or rubber that forces the lens tubes against the support tube witha minimum of axial forces. The flexible spring could either be infrictional contact with the lens tube, e.g. the lens tube is movingwithin a slot in the support tube, or fixed directly to the lens tube,e.g. a thin metal wire that can easily bend in the axial direction.Another solution that could be used in particular cases is bias forcescreated by permanent magnets.

[0029] In one embodiment, shown in FIG. 4a, the rails 31 and 32 can beconstructed having a wedge shaped cross section which narrows radiallyinward towards the axis of the system. The piezoelectric elements 13-16are mounted on opposing surfaces of U-shaped flexible printed circuitboards 18 and 19 with a rail 31 or 32 in between. In this manner, thepiezoelectric elements are positioned for engagement with the taperedsides of the rail. Spring clips 20 and 21 are provided in which aresecured the printed circuit boards 18 and 19. The spring clips 20 and 21exert a spring force on the printed circuit boards to bias thepiezoelectric elements into engagement with their respective rail. Thisbias force also has a radial component which is applied outward on thetube element to maintain the tubes in axial alignment and minimizebinding. Optical sensors 42 and 43 are mounted on the U-shaped printedcircuit boards in optical communication with reflective surfaces 44 and45 of respective lens tubes 4 and 5. As shown in FIG. 3, sensor ports 46(not shown) and 47 are provided in support tube 7 to provide access forthe optical sensors 42 and 43. The optical sensors are responsive toprovide a position indication for the lens tubes as they are moved byactuators 13-16. Optical sensors are shown for illustration, but othertypes of position sensors may be adapted for the same purpose, forexample, a resistive position sensor.

[0030] For illustration of the basic structure of this invention, twolens tubes are shown, however, it should be understood, that morecomplex lens configurations may be constructed which would require agreater number of lens tubes. Multiple lens tubes may be nested forrelative movement and driven as shown and described in this application.Each of the lens tubes may contain lens system comprised of multiplelens elements.

[0031] In one embodiment, the rails are positioned concentrically on thetube assembly, as shown in FIG. 1. In a second embodiment the rails arepositioned in the same quadrant of the tube assembly circumference, asshown in FIGS. 5 and 6. In the latter embodiment the engagement forcesare applied eccentrically to the tube elements. To assist in maintainingtube alignment, wedge shaped grooves 150 and 151 and mating surfaces 152and 153 are formed on the engaging surfaces of the lens tube assemblyand the support tube, as shown in FIG. 6.

[0032] Referring FIG. 5, the optical system 101 of the second embodimentis constructed with dual lens tubes 104 and 105. Lens tubes 104 containthe lenses of the optical system 101 mounted within support tube 107. Acover tube 121 encloses the optical assembly. More lens tubes could beemployed if a more complex optical system, i.e., more lenses, isdesired.

[0033] Similarly to the first embodiment, the optical system 101 ismounted on printed circuit board 108 to transmit light from an image(not shown) to an image sensor 110 at an image plane 111. The printedcircuit board may also contain the control circuit 162 for the digitalcamera and provide means to connect the optical system to a power sourcesuch as a battery.

[0034] Lens tubes 104 and 105 are nested for movement along axis y-ywithin support tube 107. This movement includes sliding movement of lenstube 105 relative to lens tube 104 and movement of the lens tube 104within support tube 107. In the embodiment of FIGS. 5 and 6, the lenstubes are nested in a different manner. Lens tube 104 has only a partialtubular surface 152 which has an outer surface 150 for engagement with agroove 151 on the inner surface of passage 112 in support tube 107. Theengaging surfaces provide a track in which the lens tube 104 is moved bythe action of piezoelectric elements 115 and 116. A rail 131 isconstructed on the surface 152, extending radially upward according toFIG. 6. Rail 131 extends through a slot 137 constructed for this purposein support tube 107. Rail 131 is shaped with a wedge shaped crosssection which provides surfaces for the engagement of the piezoelectricactuators 115 and 116. These slanted surfaces 155 and 156 cause theengagement force of the piezoelectric actuators 115 and 116 to apply aradial outward component of force, which tends to maintain alignment ofthe lens tube 104 within the groove 151.

[0035] Lens tube 105 may be assembled by insertion through opening 157in support tube 107 in a motion transverse to the axis y-y. Lens tube105 is also constructed with an engagement surface 154 which extendsaxially on its outer periphery. A groove 153 is constructed in the innersurface of passage 112 approximately 90° from groove 152 to receiveengagement surface 154. A rail 132 extends radially outward from surface154 through a slot 158 constructed in support tube 107.

[0036] In a manner similar to the first embodiment piezoelectricactuators 113-116 are mounted on the opposing surfaces of U-shapedprinted circuit boards 117 and 118. Circuit boards 117 and 118 aresecured to support tube 107 by spring clips 119 and 120. A pair ofoutward extending flanges 160 and 161 may be formed on support tube 107to receive printed circuit boards 117 and 118. Clips 119 and 120 engagethe flanges to secure the circuit boards in place. As shown in FIG. 6,piezoelectric actuators 115 and 116 engage slanted surfaces 155 and 156of rail 131 and are urged into engagement by bias force exerted byspring clip 119. The radial component of this force urges the opticaltube 104 outward and into engagement with groove 152. An identicalassembly secures the piezoelectric actuators 113 and 114 on support tube107 and urges the actuators into engagement with rail 132.

[0037] The configuration and operation of the piezoelectric elements aredescribed in more detail in the parent application referenced above andincorporated herein.

We claim:
 1. An adjustable support for an optical system of a digitalcamera comprising: a support tube having a longitudinal axis, saidsupport tube being secured within said camera; a first lens tube inwhich at least one lens element is fixed, said first lens tube beingmounted for relative movement coaxially on said support tube; a driverail fixed to said first lens tube and extending radially outwardtherefrom through a slot constructed in said support tube; and at leastone piezoelectric actuator mounted on said support tube in operativeassociation with said drive rail, wherein said at least onepiezoelectric actuator engages said drive rail to cause movement of saidfirst lens tube along said axis.
 2. An adjustable support for an opticalsystem of a digital camera, as described in claim 1, wherein said atleast one piezoelectric actuator is mounted on a flexible printedcircuit board.
 3. An adjustable support for an optical system of adigital camera, as described in claim 2, wherein said printed circuitboard is substantially U-shaped and further comprising: a pair ofpiezoelectric actuators mounted on opposing surfaces of said U-shapedprinted circuit board wherein said U-shaped printed circuit board ismounted on said support tube with said drive rail extending between saidactuators.
 4. An adjustable support for an optical system of a digitalcamera, as described in claim 1, wherein the supporting surfaces betweensaid lens tube and the supporting tube is very close to, or centeredwith, the engagement pads of the drive elements.
 5. An adjustablesupport for an optical system of a digital camera, as described in claim1, wherein said lens tube is forced against said support tube by springforces in the radial direction.
 6. An adjustable support for an opticalsystem of a digital camera, as described in claim 1, wherein said lenstube is forced against said support with magnetic forces in the radialdirection.
 7. An adjustable support for an optical system of a digitalcamera, as described in claim 1, wherein said drive rail is constructedwith a wedge-shaped cross section having inclined engagement surfaces,wherein engagement of said at least one piezoelectric actuator exerts aradially outward force.
 8. An adjustable support for an optical systemof a digital camera, as described in claim 1, further comprising aposition sensor mounted on said support tube in operative associationwith said first lens tube to monitor the axial position of said firstlens tube.
 9. An adjustable support for an optical system of a digitalcamera, as described in claim 8, wherein said position sensor comprisesan optical sensor in line of sight communication with said first lenstube through said support tube.
 10. An adjustable support for an opticalsystem of a digital camera, as described in claim 8, wherein saidposition sensor is mounted on said flexible printed circuit board. 11.An adjustable support for an optical system of a digital camera, asdescribed in claim 3, wherein said drive rail is constructed with awedge-shaped cross section having inclined engagement surfaces; andfurther comprising a spring clip for securing said U-shaped printedcircuit board to said support tube in a manner to exert a bias force onsaid U-shaped printed circuit board in a manner which tends to urge saidpiezoelectric actuators into engagement with said drive rail and therebyexert a radially outward force on said drive rail.
 12. An adjustablesupport for an optical system of a digital camera, as described in claim1, further comprising: a second lens tube in which at least one lenselement is fixed, said second lens tube being mounted on said supporttube for axial movement relative to said first lens tube; a second driverail fixed to said second lens tube and extending radially outwardtherefrom through a slot constructed in said support tube; and at leastone piezoelectric actuator mounted on said support tube in operativeassociation with said second drive rail, wherein said at least onepiezoelectric actuator engages said second drive rail to cause movementof said second lens tube along said axis relative to said first lenstube.
 13. An adjustable support for an optical system of a digitalcamera, as described in claim 12, further comprising: multipleprojections extending radially outward from said second lens tube;travel grooves constructed in said first lens tube to receive theprojections of said second lens tube for axial motion in said grooves.14. An adjustable support for an optical system of a digital camera, asdescribed in claim 13, wherein said projections and said travel groovesare constructed within mating surfaces which are beveled in order tomaintain a consistent radial position of said second lens tube withinsaid first lens tube.
 15. An adjustable support for an optical system ofa digital camera, as described in claim 1, wherein said at least onepiezoelectric actuator in operative association with said second lenstube is mounted on a second flexible printed circuit board.
 16. Anadjustable support for an optical system of a digital camera, asdescribed in claim 15, wherein said second flexible printed circuitboard is substantially U-shaped and further comprising: a pair ofpiezoelectric actuators mounted on opposing surfaces of said U-shapedprinted circuit board wherein said U-shaped printed circuit board ismounted on said support tube with said second drive rail extendingbetween said actuators.
 17. An adjustable support for an optical systemof a digital camera, as described in claim 12, wherein said second driverail is constructed with a wedge-shaped cross section having inclinedengagement surfaces, wherein engagement of said at least onepiezoelectric actuator exerts a radially outward force on said seconddrive rail.
 18. An adjustable support for an optical system of a digitalcamera, as described in claim 12, further comprising a second positionsensor mounted on said support tube in operative association with saidsecond lens tube to monitor the axial position of said second lens tube.19. An adjustable support for an optical system of a digital camera, asdescribed in claim 18, wherein said second position sensor comprises anoptical sensor in line of sight communication with said second lens tubethrough said support tube.
 20. An adjustable support for an opticalsystem of a digital camera, as described in claim 18, wherein saidsecond position sensor is mounted on said second flexible printedcircuit board.
 21. An adjustable support for an optical system of adigital camera, as described in claim 16, wherein said second drive railis constructed with a wedge-shaped cross section having inclinedengagement surfaces; and further comprising a spring clip for securingsaid second U-shaped printed circuit board to said support tube in amanner to exert a bias force on said second U-shaped printed circuitboard in a manner which tends to urge said piezoelectric actuators intoengagement with said second drive rail and thereby exert a radiallyoutward force on said second drive rail.
 22. An adjustable support foran optical system of a digital camera, as described in claim 12, whereinsaid first and second drive rails are spaced symmetrically around theperiphery of said support tube.
 23. An adjustable support for an opticalsystem of a digital camera comprising: a support tube having alongitudinal axis, said support tube being secured within said camera; afirst and second lens tubes each having a lens system fixed therein,said first and second lens tubes being mounted for relative movementcoaxially on said support tube; first and second drive rails fixed tosaid first and second lens tubes respectively, each of said drive railsextending radially outward from respective lens tubes through a slotconstructed in said support tube; and at least two piezoelectricactuators mounted on said support tube in operative association withsaid first and second drive rails, wherein said at least twopiezoelectric actuators engage said first and second drive rails tocause axial movement of said first and second lens tubes relative tosaid support tube.
 24. An adjustable support for an optical system of adigital camera, as described in claim 23, wherein said first and seconddrive rails are spaced symmetrically around the periphery of saidsupport tube.
 25. An adjustable support for an optical system of adigital camera, as described in claim 23, wherein said first and seconddrive rails are spaced asymmetrically around the periphery of saidsupport tube.
 26. An adjustable support for an optical system of adigital camera, as described in claim 23, wherein said support tube andsaid first lens tube are constructed with aligned spaces to allow saidsecond lens tube to be assembled in a motion transverse to said supporttube axis.
 27. An adjustable support for an optical system of a digitalcamera, as described in claim 23, further comprising: a projectionextending radially outward from each of said first and second lenstubes; a pair of travel grooves constructed in said support tube toreceive the projections of said first and second lens tubes for axialmotion in said grooves; and wherein said projections and said travelgrooves are constructed within mating surfaces which are beveled inorder to maintain a consistent radial position of said first and secondlens tubes within said support tube.
 28. An adjustable support for anoptical system of a digital camera, as described in claim 27, whereinsaid first and second drive rails are constructed with a wedge-shapedcross section having inclined engagement surfaces, wherein engagement ofsaid piezoelectric actuators exert a radially outward forces on saidfirst and second drive rail to maintain engagement between saidprojections of said first and second lens tubes and said travel grooves.29. An adjustable support for an optical system of a digital camera, asdescribed in claim 23, wherein said at piezoelectric actuators inoperative association with said first and second lens tubes are mountedon a separate flexible printed circuit boards mounted on said supporttube.
 30. An adjustable support for an optical system of a digitalcamera, as described in claim 29, wherein said flexible printed circuitboards are substantially U-shaped and further comprising: a pair ofpiezoelectric actuators mounted on opposing surfaces of each of saidU-shaped printed circuit boards, wherein said U-shaped printed circuitboards are mounted on said support tube with said first and second driverails extending between said actuators.
 31. An adjustable support for anoptical system of a digital camera, as described in claim 23, whereinsaid drive rails are constructed with a wedge-shaped cross sectionhaving inclined engagement surfaces, wherein engagement of said atpiezoelectric actuators with said drive rails exerts a radially outwardforce on said drive rails.
 32. An adjustable support for an opticalsystem of a digital camera, as described in claim 23, further comprisinga pair of position sensors mounted on said support tube in operativeassociation with said first and second lens tubes to monitor the axialposition of said first second lens tubes.
 33. An adjustable support foran optical system of a digital camera, as described in claim 32, whereinsaid position sensors comprise optical sensors in line of sightcommunication with said first and second lens tubes through said supporttube.
 34. An adjustable support for an optical system of a digitalcamera, as described in claim 32, wherein said position sensors aremounted on said first and second flexible printed circuit boards.
 35. Anadjustable support for an optical system of a digital camera, asdescribed in claim 30, wherein said first and second drive rails areconstructed with wedge-shaped cross sections having inclined engagementsurfaces; and further comprising a spring clip for securing said secondU-shaped printed circuit board to said support tube in a manner to exerta bias force on said second U-shaped printed circuit board in a mannerwhich tends to urge said piezoelectric actuators into engagement withsaid second drive rail and thereby exert a radially outward force onsaid second drive rail.